The present invention relates to high-speed receivers and detectors. More particularly, this invention relates to a scalable high-speed receiver that uses a set of sensors operating in parallel that are magnetically coupled to a transmission line to gather data from a high-speed information signal carried on the transmission line.
Today's high-speed communication networks are capable of sending data over transmission lines at extremely high data rates. Pushing far past the speeds of telephone company T1 lines carrying data at a comparative crawl (approximately 1.5 Mbps), high-speed transmitters using optical fiber transmission lines support data rates of 10 to over 100 Gigabits per second (Gbps). Defined standards already exist for extremely high data rates, including the optical carrier (OC) network standards OC-3 (155 Megabits per second (Mbps)), OC-12, (622 Mbps), OC-48 (2.5 Gbps), OC-192 (10 Gbps), and OC-768 (40 Gbps). SONET (synchronous optical network) networks running at OC-12 and OC-48 rates are becoming common, and data intensive full screen video conferencing will require OC-192 and OC-768 networks. Virtually all data intensive applications benefit from increased network speeds, and these applications may use high-speed transmitters to place any combination of analog or digital data on the communication network. Such data may come from diverse sources, ranging anywhere from Internet data transfers and telephone conversations to television signals. The data travelling down the transmission line may generally be conceptualized as an information signal passing through the transmission line, with the amplitude of the information wave at each point in the line varying in time as the information wave travels by. Accurately gathering the data contained in the information signal while the data travels at full speed is generally more difficult than simply placing the information signal on the transmission line.
Constructing receivers for high-speed communication networks is difficult because of the extremely high data rates involved. FIG. 1 shows the disparity in typical speeds achieved in today's receivers and today's fiber transmitters. Optical sensors are limited to sensing speeds of approximately 10 Gbps and receiver/demultiplexer electronics are limited to operating speeds of approximately 1 Gbps. Regardless of whether the receiver could accurately gather all the information at full speed, the receiver would often have to convert the data rate to a slower output data rate in order to accommodate the maximum operating speed of the device handling the data (for example, a desktop computer). Many popular desktop computer microprocessors are currently limited to data bus speeds that are far slower than the maximum fiber optic communication network data rate. For example, Intel Pentium.TM. processors are typically limited to 66 MegaHertz (MHz) bus speeds, while Cyrix.TM. processors may run their data bus at up to 75 MHz. These speeds are orders of magnitude slower than the maximum fiber optic communication network data rate. And, of course, since a significant portion of a microprocessor's time is spent fetching code and handling other tasks that require the data bus, the full data bus bandwidth is not ordinarily available for dedicated data processing. As a result of the disparity in processing and receive speeds, designers have expended much effort, with limited success, in designing receivers that can handle the highest speed communications networks.
In the past, most attempts at constructing high-speed receivers have centered on using sensors spaced along the transmission line to detect and gather data contained in the information signal. As the information signal travels down the transmission line, the sensors are activated in parallel to capture the data in the information signal at each sensor location at the time the sensors are activated. The sensors are usually constructed from very fast semiconductor electronics in order to support high-speed information signals. These sensors commonly use high-speed transistors constructed from expensive materials like Gallium Arsenide and Indium Phosphide. The physical properties underlying these materials allow the transistors to switch faster and therefore to gather data at higher rates than typical silicon transistors. The high-speed transistors may also perform rudimentary manipulations on the gathered data, such as sorting the data into parallel outputs at slower data rates. Unfortunately, even these high-speed transistors face severe limitations that reduce their effectiveness and prevent them from offering a practical high-speed receiver solution. Not only are the high-speed transistors currently unable to approach switching speeds nearing that of the fastest optical fiber communications network data rates, but as their structure is modified to attempt higher switching speeds, they also become more difficult to manufacture, suffer from lower yields, drive up costs, consume more power, and generate more heat. Furthermore, many common high-speed receiver designs also lead to destructive read out of the information signal. Destructive readout occurs when the operation of the sensors spaced along the transmission line significantly degrades the characteristics of the information signal as it passes by the sensors. Destructive readout prevents further information retrieval or manipulation of the information signal.
U.S. Pat. No. 5,479,120 to McEwan discloses a conventional high speed receiver having a plurality of sampler banks. Each bank comprises a sample transmission line for transmitting an input signal, a strobe transmission line for transmitting a strobe signal, and a plurality of sampling gates at respective positions along the sample transmission line for sampling the input signal in response to the strobe signal.
However, McEwan's high-speed receiver uses direct physical contacts that connect the sensors with the transmission line. The contacts connect the information detector sensors with the information signal itself as it travels down the transmission line. However, McEwan's contacts create destructive parasitic capacitance and inductive loading on the transmission line, making it harder to drive an information signal onto the transmission line and degrading the signal quality of the information signal once it is placed on the transmission line and as it travels down the transmission line. Furthermore, when the sensors operate to capture the data contained in the information signal, they disturb current flow in the transmission line, further damaging the information signal and producing perturbations of the information signal (commonly called "kickouts"). Kickouts can travel down the transmission line backward to previous sensors and forward to subsequent sensors and thereby affect data capture at other sensor contacts. As a result of the foregoing difficulties, direct physical connection of sensors to the transmission line invariably requires additional components to link the sensor with the transmission line, while providing over-voltage and current protection, and suppressing kickouts. These additional components, of course, increase the size, power consumption, and cost of the receiver.
A need remains for an improved high speed receiver. It is an object of the present invention to meet this need.